This invention relates generally to the planarization of semiconductor substrates, and more particularly to the conditioning of polishing pads.
Integrated circuits are typically formed on substrates, particularly silicon wafers, by the sequential deposition of conductive, semiconductive or insulative layers. After each layer is deposited, the layer is etched to create circuitry features. As a series of layers are sequentially deposited and etched, the outer or uppermost surface of the substrate, i.e., the exposed surface of the substrate, becomes successively less planar. This non-planar outer surface presents a problem for the integrated circuit manufacturer as a non-planar surface can prevent proper focusing of the photolithography apparatus. Therefore, there is a need to planarize the substrate surface to provide a planar surface. Planarization, in effect, polishes away a non-planar, outer surface, whether a conductive, semiconductive or insulative layer, to form a relatively flat, smooth surface.
Chemical mechanical polishing (xe2x80x9cCMPxe2x80x9d) is one accepted method of planarization. This planarization method typically requires that the substrate be mounted on a carrier or polishing head, with the surface of the substrate to be polished exposed. The substrate is then placed against a rotating polishing pad. The carrier head may also rotate and/or oscillate to provide additional motion between the substrate and polishing surface. Further, polishing slurry, including an abrasive and at least one chemically reactive agent, may be spread on the polishing pad to provide an abrasive chemical solution at the interface between the pad and substrate. In some specific applications the abrasive is entrained in, affixed to the surface of, the polishing pad.
Important factors in the chemical mechanical polishing process are: substrate surface planarity and uniformity, and the polishing rate. Inadequate planarity and uniformity can produce substrate defects. The polishing rate sets the time needed to polish a layer. Thus, it sets the maximum throughput of the polishing apparatus.
In one embodiment, a chemical mechanical polishing apparatus includes a polishing pad. The pad conditioner includes a static conditioner head having a surface area configured to contact and condition the pad. The surface area has a first end proximate to an axis of rotation of the pad and a second end remote from the axis of rotation of the pad. The first end defines a first arc length, and the second end defines a second arc lengths where the first arc length and the second arc length are substantially identical.
In another embodiment, a chemical mechanical polishing apparatus includes a polishing pad, a wafer carrier carrying a wafer to be polished, and a pad conditioner including a static conditioner head having a surface area configured to contact and condition the pad. The static conditioner head is held at a fixed position. The surface area has a first end proximate to an axis of rotation of the pad and a second end remote from the axis of rotation of the pad. The first end defines a first arc length S1=R1xcex81 and the second end defines a second arc length S2=R2xcex82, where R is a radii from the axis of rotation and xcex8 is an angle subtending an arc section corresponding to the R, wherein S1 is substantially identical to S2.
In another embodiment, a chemical mechanical polishing apparatus includes a polishing pad. The pad conditioner includes a static conditioner head having a surface area configured to contact and condition the pad. The surface area has a first end proximate to an axis of rotation of the pad and a second end remote from the axis of rotation of the pad. The first end defines a first width, and the second end defines a second width, where the first width is greater than the second width.
In another embodiment, a pad conditioner includes a static conditioner head having a non-smooth surface area to contact and condition the pad The surface area has a first end proximate to an axis of rotation of the pad and a second end remote from the axis of rotation of the pad. The first end defines a first arc length, and the second end defines a second arc length, where the first arc length and the second arc length are substantially identical.
In yet another embodiment, a method for operating a polishing apparatus includes polishing a wafer on a polishing pad rotating about an axis at a given speed. Slurry having a chemical agent and an abrasive agent to facilitate the wafer polishing is provided. A non-smooth area of a static conditioner head is contacted to the polishing pad to condition the polishing pad. The conditioner head is held at a fixed position. The non-smooth surface area has a first end proximate to the axis and a second end remote from the axis. The first end defines a first arc length, and the second end defines a second arc length, where the first arc length and the second arc length are substantially identical.